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Let $Z$ be a finite set of $s$ points in the projective space $mathbb{P}^n$ over an algebraically closed field $F$. For each positive integer $m$, let $alpha(mZ)$ denote the smallest degree of nonzero homogeneous polynomials in $F[x_0,ldots,x_n]$ that vanish to order at least $m$ at every point of $Z$. The Waldschmidt constant $widehat{alpha}(Z)$ of $Z$ is defined by the limit [ widehat{alpha}(Z)=lim_{m to infty}frac{alpha(mZ)}{m}. ] Demailly conjectured that [ widehat{alpha}(Z)geqfrac{alpha(mZ)+n-1}{m+n-1}. ] Recently, Malara, Szemberg, and Szpond established Demaillys conjecture when $Z$ is very general and [ lfloorsqrt[n]{s}rfloor-2geq m-1. ] Here we improve their result and show that Demaillys conjecture holds if $Z$ is very general and [ lfloorsqrt[n]{s}rfloor-2ge frac{2varepsilon}{n-1}(m-1), ] where $0le varepsilon<1$ is the fractional part of $sqrt[n]{s}$. In particular, for $s$ very general points where $sqrt[n]{s}inmathbb{N}$ (namely $varepsilon=0$), Demaillys conjecture holds for all $minmathbb{N}$. We also show that Demaillys conjecture holds if $Z$ is very general and [ sgemax{n+7,2^n}, ] assuming the Nagata-Iarrobino conjecture $widehat{alpha}(Z)gesqrt[n]{s}$.
We propose a new theory of (non-split) P^n-functors. These are F: A -> B for which the adjunction monad RF is a repeated extension of Id_A by powers of an autoequivalence H and three conditions are satisfied: the monad condition, the adjoints conditi
This is an appendix to the recent paper of Favacchio and Guardo. In these notes we describe explicitly a minimal bigraded free resolution and the bigraded Hilbert function of a set of 3 fat points whose support is an almost complete intersection (ACI
Mustac{t}u{a} has given a conjecture for the graded Betti numbers in the minimal free resolution of the ideal of a general set of points on an irreducible projective algebraic variety. For surfaces in $mathbb P^3$ this conjecture has been proven for
We compute the $GL_{r+1}$-equivariant Chow class of the $GL_{r+1}$-orbit closure of any point $(x_1, ldots, x_n) in (mathbb{P}^r)^n$ in terms of the rank polytope of the matroid represented by $x_1, ldots, x_n in mathbb{P}^r$. Using these classes and
A projectively normal Calabi-Yau threefold $X subseteq mathbb{P}^n$ has an ideal $I_X$ which is arithmetically Gorenstein, of Castelnuovo-Mumford regularity four. Such ideals have been intensively studied when $I_X$ is a complete intersection, as wel